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Transformer winding

Posted: Sat Feb 01, 2003 3:44 pm
by forrestgump
I have been looking for some online resources for making homemade transformers. In particular in the 1000 to 1500 volt range. I wish to make a small arc about ¼ of an inch.
I have found some commercial site however I am looking for a more do it your self site. I have access to a machine shop for fabricating a core.
Thanks in advance
Mark

Re: Transformer winding

Posted: Sun Feb 02, 2003 3:57 am
by Joseph
How much power do you need? One way to get that voltage is to use several small transformers. Put the secondaries of 10 12VAC transformers in series and connect them to 120VAC. Take the output voltage from the primaries connected in series.

Re: Transformer winding

Posted: Sun Feb 02, 2003 2:56 pm
by Dean Huster
At first, that method sounds good, Joe, especially in theory. However, if you end up grounding one side of your series-connected secondary, you'll stress the primary-to-secondary insulation of the transformers on the top end where there will be a 1200v rms potential difference and they could easily arc over.<p>Dean

Re: Transformer winding

Posted: Sun Feb 02, 2003 4:04 pm
by Externet
Hi.
1000-1500 V may not be enough for a ¼" spark. If you settle for an already made, an automobile or motorcycle ignition transformer fed with about 6-12V volts should work; or dissasemble one and rewind with less secondary turns, as you will have the core and wire.
Miguel

Re: Transformer winding

Posted: Mon Feb 03, 2003 4:56 pm
by Edd
OK jello<p>Generally accepted spec on dielectric strength of DRY air is 3 KV per MM, so your specified 1-1.5 KV would be woefully deficient for a 1/4 in sparks spacing.<p>I certainly wouldn’t look forward to the number of turns of small wire that U wud be encountering as well as the interwinding insulation in doing a self winding. Even considering this to be of a miniscule current/power level, used basically, just to show a panoramic display of sparks.
Easiest by far to utilize a cars ignition coil…circa ‘40’s-70’s used …from a junk yard for a buck a pop. as mentioned per Miguel.
For a simple yet ultra efficient circuit see :
http://home.golden.net/~kpwillia/drcirc.htm
Click on the green/red [induction coil] for a demonstration.<p>If its too hot for you, scale down the supply voltage of the unit or also you could decrease the ‘555’s PRF or PRT with the 2 pots provided.<p>
73's de Edd
[email protected] .......(Interstellar~~~Warp~~~~Speed)
[email protected]...(Firewalled-Spam*Cookies*Crumbs)
;)<p>[ February 03, 2003: Message edited by: Edd Whatley ]</p>

Re: Transformer winding

Posted: Tue Feb 04, 2003 3:36 am
by Joseph
Dean, good thinking. Even though the way I mentioned has been working for several months, I am planning to build a switching power supply which uses about 20 turns on the primary. That way, it should only need 200 turns on the secondary. Even though the voltage may not be enough to arc 1/4", it seems to do well as an electric barrier against varmits.<p>It will be important to watch the winding of the secondary to ensure that there is enough insulation at the high side of the secondary. I am planning on winding the secondary in just one pass on a toroid core with plenty of tape under the winding so that there is no arcing within the secondary or to the core.<p>I have discovered some interesting ideas and tricks for designing switching power supplies. I have some tips on switching power supply design at http://groups.yahoo.com/group/PowerSupplies/

Re: Transformer winding

Posted: Tue Feb 04, 2003 5:21 pm
by Crowbar
An oil burner ignition transformer will give you an easy 6000 - 10000 V with a 120 V input. Could easily vary the output by changing the input.

Re: Transformer winding

Posted: Sat Feb 22, 2003 1:42 am
by Joseph
Hello all,<p>I thought it important to let you know that I have changed the Web address for my switchmode power supply design information: http://groups.yahoo.com/group/switchmode/ The ealier post in this thread has the old link. Please add the new link to your favorites.<p>[ February 22, 2003: Message edited by: Joseph Meisenhelder ]</p>